Closure insert

ABSTRACT

An insert ( 1 ) for a closure provides, in a single component, a gasket function between the end panel ( 12 ) of the closure and the end sealing surface ( 22 ) of a container neck finish ( 20 ), a thread forming feature ( 3 ) and a tamper evident band ( 5 ). The sealing portion (gasket ( 2 ) and thread forming feature ( 3 )) of the insert is formed from soft pliant material so as to provide excellent sealing. The tamper evident band ( 5 ) is made from much stiffer material than that of the sealing portion, thereby providing rigidity to the entire component. During assembly the integral tamper evident band ( 5 ) thus maintains the insert in a circular and non-twisted shape, ensuring ease of handling of the insert.

[0001] This invention relates to inserts for closures of thepress-on/twist-off type which have a tamper evident band.

[0002] Press-on/twist-off closures are caps which not only are appliedto and removed from a container by press-on and twist-off actionsrespectively but which also comprise a tamper-evident band. Suchclosures are sometimes known commercially as PT⁺ (trade mark) closures.

[0003] Press-on/twist-off (PT) closures are well known in which theclosure has an insert formed from a foamed plastisol material. PT⁺closures have been described, for example, in EP-0450959 in which theclosure comprises a metal body lined with a plastisol gasket and havinga tamper-evident band (also known as a “security ring”).

[0004] In WO 98/52833, a press-on/twist-off closure is described whichuses a pre-formed insert in place of the former plastisol material.Instead of moulding the insert in the closure shell, as with a foamedplastisol material, the insert of WO 98/52833 can be formed separatelyby injection moulding, for example, and then secured in the shell by acurl on the edge of the shell.

[0005] The insert of WO 98/52833 is formed from a relatively softmaterial such as certain grades of polypropylene, polypropylene/nylonblends or thermoplastic elastomers. Soft liners provide excellentsealing since they readily conform to irregularities in the sealingsurface and threads in the finish of a glass container to which theclosure is applied. However, problems arise when applying the closuresince the insert may flex if the press-on capping action is not appliedin a truly horizontal position. This problem can be further exacerbatedif a tamper evident band is to be used in conjunction with the softinsert, as the liner is free to move in the metal shell when the tamperevident band is applied. This can lead to rotation and/or tilt of theinsert.

[0006] A further problem exhibited by the insert of WO 98/52833 is thedifficulty in handling a flexible component at commercial line speeds incurrent cap manufacturing apparatus. Twisting of the component intoloops and asymmetric shapes is typical in addition to problems ofpresenting the insert to the closure shell in the correct orientation.

[0007] This invention seeks to provide a pre-formed insert for a closurewhich overcomes these problems.

[0008] According to the present invention, there is provided apre-formed moulded insert having a first portion formed of a polymericmaterial having a Shore hardness in the range of 30 Shore A to 45 ShoreD, and a second portion comprising a tamper evident band integrallyformed with the first portion and formed of a polyolefin material.

[0009] Typically, the material of the second portion has a flexuralmodulus greater than 1200.

[0010] In a further aspect of the present invention, there is provided aclosure of the press-on/twist-off type comprising a shell including askirt and an end panel, and a pre-formed insert of the type describedabove, in which the first portion is adapted to perform liner andsealing functions in the closure, in which the insert is secured inposition with the first portion within the closure such that the tamperevident band depends from the closure shell.

[0011] For sealing a container, the thread finish on the container mayform complementary threads on the inner side wall of the insert when theclosure is applied to the container and the gasket part of the insertprovides sealing between the end panel of the closure and the endsealing surface of a neck finish. The insert of the present inventionthus provides (i) a gasket function, (ii) a thread forming feature and(iii) a tamper evident band, in a single component.

[0012] By using an insert which includes an integral tamper evident bandprior to assembly in the metal shell, risk of tilting or rotation of thesealing/liner portion is eliminated. The unitary construction of theinsert of the present invention means that there is only ever a singlecomponent to be secured in position.

[0013] The insert may be secured in position within the shell by curlingthe edge of the metal shell into or around part of the insert, thermalor other bonding, or by other mechanical means of engagement.

[0014] In a preferred embodiment, the tamper evident band portioncomprises a material having a flexural modulus of between 1200 and 1600MPa. By using a stiffer material for the tamper evident ring portion ofthe insert, rigidity is provided to the whole insert. This in turn makesthe insert easier to handle by maintaining it in a circular (rather thantwisted) shape, easier to position within the closure shell and, wheninserted in the closure shell, easier to apply to a container in therequired horizontal position.

[0015] The insert may be formed by sequential (two colour/two material)moulding of a plastic component from two portions having propertiesselected according to the portion of the insert for which the materialis intended. Usually the material of the second portion may bepolypropylene or polypropylene-based. Conventionally polymers such aspolypropylene is characterised by its modulus.

[0016] The material of the first portion may be a polypropylene blendincluding materials such as butyl rubber, nitrile rubber, EPDM, ethylvinyl, polyurethanes, acrylic polymers, polyethylenes and copolymers, ornylons. Conventionally, such elastomers are defined by their Shorehardness. The choice of material used for the first portion depends onthe ability to mould a single component from two materials withdifferent Shore hardness/flexural moduli according to the function to beperformed.

[0017] Preferred embodiments of the invention will now be described, byway of example only, with reference to the drawings in which:

[0018]FIG. 1 is a schematic sectional view of an insert of the presentinvention;

[0019]FIG. 2 is a schematic sectional view of the insert of FIG. 1 in afirst embodiment of tamper evident vacuum closure; and

[0020]FIG. 3 is a schematic sectional view of the insert of FIG. 1 in asecond embodiment of tamper evident vacuum closure.

[0021] Referring to FIG. 1, a pre-formed insert is shown generally at 1,and comprises a first portion having a sealing part 2 and a threadretention part 3, a securing rim 4 and a tamper evident band 5. Theinsert is typically formed by sequential injection moulding of thetamper evident band 5 and then the sealing/thread retention portion, orvice versa.

[0022] The material of the sealing/thread retention portion is selectedfor its ability to retain the impression of the thread on a glasscontainer, and for optimum sealing. The Applicant has found that whilstmaterials having a Shore D hardness of up to 90 are, in theory,suitable, there is an incidence of “slow leakers” which reducesconsiderably with the hardness. However, handling of materials having alow Shore D hardness of less than, say, 80 is much more difficult atcommercial line speeds.

[0023] Nonetheless, in the present invention, the material of the secondor tamper evident band portion 5 of insert 1 is much stiffer than thatof the sealing/thread retention portion and so provides a degree ofrigidity to the insert 1. Typically the tamper evident band portion hasa flexural modulus of 1200 to 1600. For optimum sealing, the modulus ofthe sealing/thread retention portion is from 5 to 100. In contrast withthe insert of WO 98/52833, the insert 1 combines both stiff and pliablematerials in a single component, is easy to handle, does not deformduring application to a container shell and provides excellent sealing.

[0024] Two embodiments of PT+ vacuum closure 10 using the insert of thepresent invention are shown applied to the neck finish 20 of a containersuch as a glass jar in FIGS. 2 and 3. The closure has a metal shell 11,including an end panel 12 and a downwardly dependent skirt 13. The firstportion, comprising sealing and thread forming parts 2, 3 ofpolypropylene insert 1 is received within the shell 11, with tamperevident band portion 5 depending from the rim of the shell.

[0025] In the embodiment of FIG. 2, the insert 1 is applied to the shell11, and the skirt 13 is curled over to form an inwardly facing curl 14.The curl 14 traps the sealing rim 4 and secures the insert 1 within theshell. Ideally, as shown, the edge of the curl 14 is retained within agroove 7 in the tamper evident band portion 5. Alternatively, the curlmay simply embed itself in the insert material.

[0026] The insert of the embodiment of FIG. 3 is heat sealed into theshell 11 as shown at 8. Clearly other forms of bonding are also possiblewithin the scope of the invention. The insert of FIG. 3 may also includea groove 7′ so that the exposed edge of the metal shell 11 is curled andtrapped in the insert, thus increasing the mechanical lock and avoidingexposure to the atmosphere.

[0027] The neck finish 20 of the container includes thread formations 21and an end sealing surface 22. When the vacuum closure is applied to theneck finish in a conventional manner, the sealing part 2 of the insert 1forms an hermetic seal between the end panel 12 and the end sealingsurface 22 of the container at Area ‘A’ (see FIG. 3). Typically a sideseal is also formed between a region of the insert and the neck finishat Area ‘B’. Similarly, a lower region of the insert 1 co-operates withthe side wall of the neck finish at Area ‘C’, in order to provide abarrier to the ingress of foreign bodies such as dust, dirt and insectsetc.

[0028] The thread retention part 3 of the insert is deformed by thethread formations 21 on the neck finish so that the vacuum closure 10can be removed from the container by the user in a “twist-off” manner.The thread retaining portion 3 of the insert 1 remains at leastpartially deformed by the thread formations 21, so that the closure canbe reapplied to the glass jar by twisting it back on to the neck finish.

[0029] In the embodiments shown in FIGS. 2 and 3, the insert 1 isprovided with pre-formed longitudinally extending ribs 6. The ribs aretypically 0.35 mm in radial depth as compared to an overall insertradial thickness of 0.6 mm. The thread formations 21 make indentationsin the ribs 6 which allow the closure to be easily reapplied to thecontainer, whilst ensuring that the initial opening torque necessary toremove the closure from the container is not excessive and typically inthe range 10-30 Kgf-cm. The ribs 6 also act as a cushion, so as toimprove the abuse resistance of the closure. Other forms of projections,such as pimples etc. (not shown) could also be employed to retain theimpression of the thread formations 21 and so as to ensure that theclosure ‘ramps off’ when twisted.

[0030] The tamper evident band includes a line of weakness (not shown)which fractures when the closure is removed from the container. Ideally,this is formed by cutting into the tamper evident band portion of theinsert after it has been fitted to a closure. The line of weakening maybe made in any known manner, for example as disclosed in EP-0784575.

1. A pre-formed moulded insert having a first portion formed of apolymeric material having a Shore hardness in the range of 30 Shore A to45 Shore D, and a second portion comprising a tamper evident bandintegrally formed with the first portion and formed of a polyolefinmaterial.
 2. An insert according to claim 1, in which the second portioncomprises a material having a flexural modulus of between 1200 and 1600MPa.
 3. An insert according to claim 1 or claim 2, which is formed bysequential moulding.
 4. A closure of the press-on/twist-off typecomprising a shell including a skirt and an end panel, and a preformedinsert according to any one of claims 1 to 3, in which the first portionis adapted to perform liner and sealing functions in the closure, andthe insert is secured in position with the first portion within theclosure such that the tamper evident band depends from the closureshell.
 5. A closure according to claim 4, in which the thread finish ona container forms complementary threads on the insert when the closureis applied to the container.
 6. A closure according to claim 4 or claim5, in which the insert is secured in position within the shell bymechanical engagement.
 7. A closure according to claim 6, in which themechanical engagement is curling the edge of the metal shell into oraround part of the insert.
 8. A closure according to claim 6 or claim 7,in which the mechanical engagement is thermal or other bonding.